(a) Field of the Invention
The present invention relates to a thermoplastic transparent resin composition, and more particularly, to a thermoplastic transparent resin composition which is resistant to shocks, chemically resistant, easily processed, and highly transparent. The present invention also relates to a method for manufacturing the thermoplastic transparent resin composition in which, when performing graft copolymerization of a methacrylic acid or an acrylic alkylester compound, an aromatic vinyl compound, and a vinylcian compound in a mixture of a small aperture polybutadiene rubber latex and a large aperture polybutadiene rubber latex, both having a suitable gel content, a refraction coefficient is maximized by controlling the mixture ratio of these monomers, thereby realizing the advantages of the resin composition stated above.
(b) Description of the Related Art
Many various products today use transparent plastic parts for both practical reasons and to provide distinguishable characteristics to a product. Examples include the plastic screen cover on a cell phone, a washing machine cover that enables the user to view the contents being washed, portions of the housing of a PC monitor, pager housings, the housings and covers of home appliances, etc. However, the typically used ABS (acrylonitrile-butadiene styrene) copolymer resin, although providing good shock resistance, chemical resistance, processability, and surface gloss, has limited transparency.
The following are some of the methods for providing transparency in plastic materials:
1) A method using transparent polycarbonate resin.
2) A method of providing shock resistance to transparent PMMA polymethylmethacrylate) resin (U.S. Pat. No. 3,787,522, Japanese Patent No. Sho 63-42940).
3) A method of providing transparency to HIPS (high impact polystyrene) resin (European Patent No. 0,703,252).
However, in the method of using polycarbonate resin, although this material has good transparency and shock resistance at room temperature, it is not highly resistant to chemicals and does not display high resistance to shocks at low temperatures. This material also has problems related to processability, making it difficult to manufacture this product to large sizes. With regard to PMMA resin, though providing good transparency and processability, this material has an extremely low level of resistance against shocks. Finally, regarding HIPS resin, this material has a low level of resistance against chemicals and is easily scratched.
U.S. Pat. No. 4,767,833, in an effort to solve the above problems, discloses a transparent resin in which monomers such as methylmethacrylate, styrene and acrylonitrile are graft copolymerized in SBR (styrene-butadiene rubber) latex such that properties of shock resistance, chemical resistance, and processability are realized. However, this resin is limited in its resistance to shocks at low temperatures and displays a limited degree of transparency.